Although CAT5e is ok for up to 100 metres(ish), I would not reccomend running it under carpets etc. the CAT5 spec relies on the twist of the pairs to reduce capacitance and crosstalk, if a cable becomes deformed or damaged by traffic over it, thiswould cause a slowdown in performance at best or dropped / corrupted packets before the link failed completely. note that a 'lights on' link does not necassarily indicate a correctly operating link. I have used a flat CAT5e cable before for this purpose, although this was from a UK manufacturer and was not cheap, it also requires special termination boxes. If you have cavity floors, is it possible to feed standard CAT5e through this ?
Cheers,
10forcash